The action starts at a theme park, where Darren is having a fun day out with his parents and his little brother.
But that soon becomes just a happy memory. Darren's parents are having LOTS of arguments at home.
Darren and his brother try to make things better. They write their parents a note, saying that they will stop arguing with each other.
The arguments don't stop. On fireworks night, Darren's mum reveals to him that she's splitting up with his dad.
Darren is devastated. He's really upset that his dad is leaving the family home.
Darren can't get the problem out of his mind. He locks himself in the school toilet - to have a cry.
But he soon starts to get his head around the situation, even offering support to a friend whose parents have split as well.
As part of the new arrangement, Darren and his brother see their dad regularly.
Darren feels all right. He's glad that the rows have stopped.
He's learning to cope with his parents breaking up - and decides to re-name his diary: "NOT The Worst Thing Ever."